Septic Tank Installation near you

The Environment Agency decides whether connecting to a public foul sewer is reasonable, and it weighs how close you are to one, the cost of connecting compared with the cost of installing a treatment system, whether anything in the landscape such as a major road would prevent a connection, and whether your proposed system would have environmental benefits, for example by reusing treated effluent. If connecting is reasonable, no permit will be granted for a private system.

For discharges started on or after 1 January 2015 there is a hard proximity rule as well. A single domestic property cannot meet the general binding rules if there is a public foul sewer within 30 metres of any boundary of the premises the system serves. For a development of more than one property the distance scales with the number of houses — three properties gives 90 metres — and where some of the discharge is non-domestic the volume is divided by 0.75 and the result multiplied by 30 to give the distance in metres.

Get this settled before the ground is broken. Approved Document H2's own note is that initial contact with the regulator is normally made as part of the planning procedures for non-mains drainage, and that anyone seeking building regulations approval for non-mains drainage should establish what is required before applying, because the answer may have a direct bearing on the type of system that can be installed.

A drainage field can only be designed once the ground has been measured, and Approved Document H2 sets out how. First a trial hole is dug to find the standing groundwater table: a minimum of one square metre in area and two metres deep, or a minimum of 1.5 metres below the invert of the proposed drainage field pipework. The groundwater table should not rise to within one metre of the invert level of the proposed effluent distribution pipes, and if the test is done in summer the likely winter groundwater levels have to be considered.

Then the percolation test. A hole 300mm square is excavated to a depth 300mm below the proposed invert level of the effluent distribution pipe, filled to a depth of at least 300mm with water and left to seep away overnight. The next day the test section is refilled to at least 300mm and the time in seconds is observed for the water to fall from 75 per cent full to 25 per cent full, a drop of 150mm. Dividing that time by 150 gives Vp, the average time in seconds for the water to drop one millimetre.

The test should be carried out at least three times with at least two trial holes, and the average taken. It must not be done in abnormal weather — heavy rain, severe frost or drought — because the result would not represent how the ground behaves day to day. A quotation produced without this exercise is a guess, and the guidance is equally clear that the natural vegetation on the site and a preliminary assessment in consultation with the regulator and the local authority both feed into whether the site is suitable at all.

Approved Document H2 treats a septic tank with secondary treatment as normally the most economic way of dealing with waste water from small developments of roughly one to three dwellings, and is firm that a septic tank should only ever be used together with a form of secondary treatment — a drainage field, a drainage mound or a constructed wetland. The tank alone does not finish the job; its discharge can still be harmful.

Packaged treatment works treat effluent to a higher standard than septic tank systems, which normally allows a direct discharge to a watercourse, and they tend to be the better answer where space is limited or where a septic tank and drainage field are not possible. Drainage mounds are drainage fields raised above the natural ground surface to provide an aerated layer, useful where the subsoil is occasionally waterlogged but otherwise suitable. Constructed wetlands such as reed beds can provide secondary or tertiary treatment where drainage fields are not practical.

One option is effectively closed off. The Environment Agency's guidance states that you cannot meet the general binding rules using a well or borehole to discharge waste water to ground, or a soakaway designed for rainwater installed after December 2007, and that you should avoid boreholes, shafts, concrete rings and similar structures for new discharges to ground because of the increased pollution risk. Where effluent discharges directly to groundwater through such a system, the Environment Agency will not grant a permit and the system must be replaced.

Scotland reaches similar engineering by its own route, and the numbers are not the same, so an English specification cannot simply be carried north. The Scottish building standards handbook requires every part of a private wastewater plant or septic tank to be located at least 5 metres from a dwelling, on the basis that leakage has been shown to damage foundations, and at least 5 metres from a boundary so that an adjoining plot is not inhibited from its full development potential.

Access for desludging is specified rather than left to judgement: the tanker needs a working area giving a clear route for the suction hose, not more than 25 metres from the tank where the area is no more than 4 metres higher than the tank's invert level, and able to support a vehicle axle load of 14 tonnes. The handbook also expects treatment plants to be inspected monthly, with the effluent in the outlet free-flowing.

The infiltration design is banded by percolation value: fast where Vp is not more than 15 seconds per millimetre, normal above 15 and up to 100, slow above 100 and up to 140, and very slow above 140, each band pointing to different permitted solutions. The trench area uses the same formula, A = P x Vp x 0.25, but may be reduced by 20 per cent where the waste water has had the benefit of secondary treatment followed by settlement. Location rules require an infiltration field at least 50 metres from any spring, well or borehole used as a drinking water supply, and at least 10 metres horizontally from any watercourse, permeable drain, road or railway. Above all of it sits SEPA's authorisation, which the handbook says is required for all discharges of sewage effluent.

Replacement is often driven by compliance rather than by failure. A septic tank discharging to a watercourse has to be dealt with regardless of how well it appears to work, and the three permitted routes are connecting to a public foul sewer, replacing the tank with a small sewage treatment plant, or installing a drainage field and then meeting the rules for discharges to ground. Which of those is cheapest depends almost entirely on the ground and the distance to a sewer, which is why the site assessment comes before the quotation.

Where the existing system is staying but is under-performing, size is the first thing to check. The rules require the system to be large enough for the maximum amount of sewage it needs to treat, and to be recalculated if the load increases — extending the property or connecting another one both count. Be aware that a significant change can convert an existing discharge into a new one, which brings the additional rules for discharges started on or after 2 October 2023 into play.

There is one piece of paperwork people forget at the point of replacement. If your current system never received building regulations approval when it was installed, you may need to apply for it, and you might also need planning permission; for systems installed before 1 January 2015 the guidance points you to your local council for advice on planning. Sorting that out during a planned replacement is far less painful than discovering it during a sale.

LokalMatch is the first step and nothing more: you describe the property, what the ground assessment has found and your postcode once, and septic contractors covering that area get in touch, having paid for the request. LokalMatch does not design or install anything, has no influence over what any contractor charges, and does not vet, rank or recommend the businesses that reply, so compare what each quotation actually includes — the trial hole and percolation testing, the drainage field area it is based on, the building regulations application, and putting the ground back.